It has been concluded recently that small traces of many organic halides present serious health problems, including a suspicion that many are carcinogenic agents. The detection of various organic halides in heavy concentrations presents no problem. However, a difficult problem of trace analysis and quantification is a more difficult problem. For example, petrochemical processing plants manufacturing methyl chloride, and vinyl chloride must reduce the volume of these organic halides introduced into the atmosphere for health purposes. It becomes necessary to measure trace quantities of these organic halides in the atmosphere even down to levels such as one part per billion of air, or even smaller concentrations.
It is difficult to provide laboratory equipment which is sensitive to traces of this magnitude and in particular with good specificity relative to that components of interest. The difficulty is more apparent upon departure from the use of laboratory equipment to circumstances where an apparatus must continue to operate at its place of installation indefinitely, for example at a chemical processing plant, in varied outdoor and atmospheric circumstances. It has been discovered that the difficulty in detecting trace chlorides, bromides and trace fluorides, although trace alkyl fluorides are of lesser interest, can be circumvented and yet an accurate and precise quantification thereof can be obtained through the method and apparatus of the present invention. Upon substitution of a heavier and more easily disassociated halogen for a smaller lower cross section more tightly bound halogen in many organic halides, particularly in monoalkylhalides, the sensitivity of detectors can be enhanced substantially. The precise detector utilized is subject to variation, and includes an ionization detector such as an electron capture detector, a photoionization detector, or a spectrophotometric detector. The present process works quite well even with other compounds present in the same sample to provide a quantification of the only specific compound of interest. The response of the detector is measurably enhanced by the substitution through transhalogenation of an iodide ion for a lighter convalently bound chloride or fluoride atom. The response of the electron capture method is enhanced by the replacement of fluorine, chlorine, or bromine by iodine. The increased mass results in easier detection and the formation of a larger signal provides for a more sensitive instrument and method. Also, monoalkyl iodides yield excellent resultants at lower temperatures such as room temperature, while elevated temperatures are required for improved detection of monoalkyl chlorides when using an electron capture detector.